Etiological differences in patterns of psycholinguistic development of children of IQ 30 to 60.

We compared the psycholinguistic abilities of 131 mentally retarded children (IQs 30 to 60) of different etiological classifications (Down's syndrome, biologically brain damaged, environmentally caused retardation, unknown cause) and characterized each etiology according to the different patterns of psycholinguistic skills exhibited by the children. Level of skills was determined by the Illinois Test of Psycholinguistic Abilities, which was administered to each subject. Down's syndrome children exhibited significantly lower verbal-auditory skills than visual-motor skills. The environmentally caused retardation group showed no significant differences in development of psycholinguistic channels. Down's syndrome children had significantly lower verbal-auditory abilities than did the other etiological groups of severely retarded children. Etiological differences in the visual-motor channel were less marked.